This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-249702, filed Aug. 21, 2000; and No. 2001-093303, filed Mar. 28, 2001, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an inspection method and an inspection apparatus, particularly, to an inspection method and an inspection apparatus which permit suppressing the needle pressure applied by a probe to the inspection electrode of a target object to be inspected.
2. Description of the Related Art
In the manufacturing process of semiconductor devices, these devices are formed on a semiconductor wafer. Then, inspected are the electrical characteristics of the target object(s) to be inspected (hereinafter referred to as xe2x80x9cthe devicexe2x80x9d) such as a device in the state of the semiconductor wafer and a device cut away from the semiconductor wafer and packaged. In the inspection process, the device is inspected by transmitting and receiving an electric signal to and from a tester via a probe electrically in contact with the inspection electrodes of the device.
Where the inspection electrode is formed of a material that is likely to be oxidized such as aluminum, copper or a solder, an insulating film such as an oxide film is formed on the surface of the inspection electrode in the inspecting stage. Therefore, even if the probe is brought into contact with the inspection electrode, the electrical connection between the two is not stabilized. Particularly, where the inspection electrode is made of aluminum, a very hard oxide film is formed on the surface of the inspection electrode, with the result that it is very difficult to bring the probe into electrical contact with the inspection electrode.
In the prior art, the probe is brought into electrical contact with the inspection electrode by the mode shown in FIGS. 22A and 22B in accordance with the flow chart shown in FIG. 21. Specifically, the preparation for the inspection of the device is performed first (step S1), followed by bringing the probe N into contact with the inspection electrode P with a predetermined pressure, e.g., 10 to 20 g/a probe, as shown in FIG. 22A (step S2). Then, it is judged whether or not the probe N has been brought into electrical contact with the inspection electrode P (step S3). Where it is judged that electrical contact has been achieved, the inspection is started (step S4). In general, it is judged in step S3 that the probe N is not in electrical contact with the inspection electrode P by simply bringing the probe N into contact with the inspection electrode P because an insulating film O is interposed between the two. In order to overcome the difficulty, the probe N and the inspection electrode P are reciprocated relative to each other (scrubbed) as denoted by an arrow in FIG. 22B so as to scrape off the insulating film O (step S5). In this step S5, the probe N is brought into electrical contact with the inspection electrode P. After electrical contact has been confirmed, the inspection is started in step S4.
Another method of breaking the insulating film O is to sharpen the tip of the probe. In this method, it is possible to increase the planar pressure given by the probe to the inspection electrode, making it possible to permit the probe to be stuck into the inspection electrode so as to ensure a good electrical contact between the two. In this case, it is necessary to stick the tip of the probe into the inspection electrode by at least 2,000 to 4,000 xc3x85 in order to ensure electrical contact.
Recently, proposed is a probe card having fine probes each having a diameter of scores of microns formed in a silicon substrate with a small pitch by using, for example, micro machine processing technology. Since the probe card has a micro structure, it is possible for the probe card to cope with a high speed signal. In addition, since the probe is formed on a silicon substrate, the probe card is advantageous in that it eliminates the effects caused by the difference in the thermal expansion coefficients of the probe card and the device in the heating test.
In the method of scraping off the insulating film, it is possible for the scraped dust of the insulating film to attach to the probe N, which impairs conduction. Therefore, it is not guaranteed that electrical contact between the probe and the inspection electrode can be ensured by the method described above. Further, the life of the probe N is shortened by the scrubbing and the yield of the manufactured device is lowered because the inspection electrode P is scratched as shown in FIG. 22B. It should be noted that the contact point between the probe N and the inspection electrode P set in advance at the optimum position is altered by the scrubbing. It has also been found that the device is contaminated with the scraped dust scattered from the insulating film O, as shown in FIG. 22B. Such being the situation, it is necessary to periodically remove the scraped dust of the insulating film from the probe N, leading to a reduction in the inspection efficiency.
In the method in which the tip of the probe is stuck into the inspection electrode, the damage done to the inspection electrode is small. However, the inspection electrode is scratched as in the method described above. Also required is the durability for maintaining the shape of the tip portion of the probe. Since the degree of integration of the devices has been markedly enhanced in recent years, the miniaturization of the device and the thinning of the film have been drastically progressed. Under the circumstances, the thickness of the inspection electrode has been decreased such that, if the probe is stuck until the probe is brought into electrical contact with the inspection electrode, the underlying layer of the inspection electrode also tends to be damaged.
The probe card manufactured by utilizing the micro machine processing technology has a fine probe structure, with the result that it is difficult to apply a high needle pressure to the probe.
The present invention has been achieved in an attempt to overcome at least one of the above-noted problems inherent in the prior art.
An object of an aspect of the present invention is to provide an inspection method and an inspection apparatus, which permit markedly decreasing the needle pressure applied by the probe to the measuring electrode.
Another object of an aspect of the present invention is to provide an inspection method and an inspection apparatus, which permit suppressing the damage done to the inspection electrode and which also prolong the life of the probe when used repeatedly.
Still another object of an aspect of the present invention is to provide an inspection method and an inspection apparatus which reduce the necessity of applying a cleaning treatment to the probe so as to improve the inspecting efficiency.
Additional objects and advantages of an aspect of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
According to a first aspect of the present invention, there is provided a method of inspecting a target object to be inspected, comprising the steps of:
bringing about a fritting phenomenon in a part of the insulating film formed on the inspection electrode of the target object to be inspected so as to break a part of the insulating film;
bringing an inspecting probe into electrical contact with the surface of a part of the inspection electrode, the insulating film of the part of the inspection electrode having been broken by the fritting phenomenon; and
inspecting the electrical characteristics of the target object by using a tester connected to the inspecting probe.
It is desirable for the step of breaking a part of the insulating film included in the inspection method described above to comprise the steps of:
bringing a probe into contact with the inspection electrode of the target object to be inspected; and
applying a voltage between the probe and the inspection electrode so as to bring about the fritting phenomenon in the insulating film formed on the surface of the inspection electrode.
It is also desirable for the step of breaking a part of the insulating film comprises the steps of:
bringing a first probe and a second probe into contact with the inspection electrode of the target object; and
applying a voltage between the first probe and the second probe so as to bring about the fritting phenomenon in the insulating film formed on the surface of the inspection electrode.
It is desirable for the inspection method described above to further comprise the step of inspecting the electrical characteristics of the target object to be inspected by utilizing, as the inspection electrode, at least one of the first probe and the second probe in contact with the surface of a part of the inspection electrode, the insulating film of the part having been broken by the fritting phenomenon which has been brought about within the insulating film.
In the inspection method of the present invention, it is desirable for the step of inspecting the electrical characteristics of the target object to be inspected by utilizing at least one of the first probe and the second probe as the inspecting probe to comprise the step of electrically disconnecting the probe not utilized as the inspecting probe, from at least one of the tester and the inspection electrode.
In the inspection method of the present invention, it is desirable for the step of electrically disconnecting the probe from the inspection electrode to comprise the step of electrically separating the probe not utilized as an inspecting probe from the inspection electrode.
In the inspection method of the present invention, it is desirable for the separating step to be performed by utilizing at least one of a piezo element, a bimetal, and an electrostatic element.
According to a second aspect of the present invention, there is provided an inspection apparatus of a target object to be inspected, comprising:
a power source circuit for applying a voltage to a part of the insulating film formed on the inspection electrode of the target object so as to form a predetermined potential gradient in at least a part of the insulating film, a fritting phenomenon being formed in the insulating film by the predetermined potential gradient so as to break a part of the insulating film;
an inspecting probe that is brought into electrical contact with the surface of a part of the inspection electrode, the insulating film of the part of the inspection electrode having been broken by the fritting phenomenon; and
a tester connected to the inspecting probe so as to inspect the electrical characteristics of the target object to be inspected.
It is desirable for the inspection apparatus to further comprise a current limiter for limiting the current flowing between the probe and the inspection electrode.
In the inspection apparatus of the present invention, it is desirable for the current limiter to form a predetermined potential gradient in at least a part of the insulating film to comprise:
a first probe and a second probe each brought into contact with the inspection electrode of the target object to be inspected; and
a power source circuit for applying a voltage between the first probe and the second probe, the voltage serving to bring about a fritting phenomenon in the insulating film formed on the surface of the inspection electrode.
In the inspection apparatus of the present invention, it is desirable for at least one of the first probe and the second probe to be formed of at least one material selected from the group consisting of tungsten, palladium and a beryllium-copper alloy.
It is desirable for the inspection apparatus of the present invention to further comprise a controller for controlling the power source circuit, and a communication circuit for connecting the control means to the tester.
In the inspection apparatus of the present invention, it is desirable for the means for forming a predetermined potential gradient in at least a part of the insulating film to be incorporated in the tester.
In the inspection apparatus of the present invention, it is desirable for the current limiter for limiting the current flowing between the probe and the inspection electrode to be incorporated in the tester.
In the inspection apparatus of the present invention, it is desirable for the power source circuit for forming a predetermined potential gradient in at least a part of the insulating film to comprise:
a first probe and a second probe, which are brought into contact with the inspection electrode of the target object to be inspected; and
a power source circuit for applying a voltage between the first probe and the second probe, the voltage serving to bring about a fritting phenomenon in the insulating film formed on the surface of the inspection electrode.